A novel melatonin antagonist, N-(2,4-dinitrophenyl)-5-methoxytryptamine neutralizes some effects of melatonin in the female Syrian hamster

In this present study we evaluated the ability of a recently synthesized melatonin antagonist, N-(2,4-dinitrophenyl)-5-methoxytryptamine (ML-23), to antagonize the effects of afternoon injections of melatonin on the reproductive and thyroid axes in the female Syrian hamster. Thirty-six animals were divided into four groups and treated daily for 13 weeks with an afternoon injection of melatonin (25 micrograms/injection) or saline diluent. ML-23 was given via the drinking water to both melatonin- and saline-treated groups. The experiment was continued until 78% of melatonin-treated animals exhibited acyclicity. The results show that ML-23 partially reversed the effects of melatonin on pituitary follicle-stimulating hormone concentrations but was without effect on the decreased pituitary and plasma prolactin concentrations induced by melatonin treatment. Furthermore, ML-23 antagonized the effects of melatonin on plasma thyroxine levels and significantly increased plasma triiodothyronine concentrations and the free triiodothyronine index when used in combination with melatonin. The decrease in ovarian weight and plasma estradiol, but not progesterone, obtained with melatonin treatment also was reversed by ML-23. Our data suggest that ML-23 prevents the effects of melatonin treatment on ovarian weight, pituitary follicle-stimulating hormone levels, plasma estradiol, and thyroxine concentrations in the female Syrian hamster. Since ML-23 did not prevent the effects of melatonin on pituitary weight, plasma luteinizing hormone and prolactin, and pituitary prolactin concentrations, the actions of ML-23 may involve only peripheral sites of action of melatonin. Alternatively, the dose of ML-23 may not have been optimal to prevent all of the central effects of the indoleamine.     

The influence of fish oil supplementation on plasma lipoproteins and arterial lipids in vervet monkeys with established atherosclerosis.

There is controversy about whether supplementing diets with marine fish oil can regress, promote or prevent atherosclerosis. Therefore the effects of an Atlantic pilchard oil (FO) supplement and dietary change were measured in a proven atherosclerosis model. Vervet or African Green monkeys were fed an atherogenic diet (AD) for long enough to ensure progression before treatments started. Matched groups were then treated for 20 months, either by adding FO to the AD (AD/FO), or by changing to a therapeutic diet with FO (TD/FO). Control treatments consisted of supplementing with sunflower oil (SO) instead of FO, so that treatments were AD/SO and TD/SO. The same total polyunsaturates were supplied by the FO and SO and the dose of FO was realistic (2.5% of total energy). A reference group (R) received the TD with no oil supplements. Supplementing with FO did not change the concentrations of total, low or high density lipoprotein cholesterol in plasma. After The AD/FO the intimas of aortas contained more total (p < or = 0.001), free (p < or = 0.05) and esterified (p < or = 0.05) cholesterol, total phospholipid (p < or = 0.01) and sphingomyelin (p < or = 0.05) than after the AD/SO. After FO supplementation eicosapentaenoic acid was significantly higher and arachidonic acid significantly lower in the plasma and aorta intima phosphatidylcholine. None of these changes was anti-atherogenic in terms of atherosclerosis measured in the same individuals (1). Nor did FO increase the efficacy of the TD.     

Evidence that thyroglobulin contains nonidentical half molecule subunits

Bovine thyroglobulin was extracted from unfrozen glands, purified by sucrose gradient centrifugation, and fractionated into a narrow range in iodine content by RbCl isopycnic centrifugation. The subunit composition of these preparations was studied by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The extent of dissociation of 19 S into 12 S half-molecules followed the known relationship with iodine, i.e. decreased dissociability of 19 S with increased iodine content. The undissociated 19 S band always consisted of three closely spaced, equidistant bands. Reduction of the disulfide bonds of thyroglobulin by mercaptoethanol in SDS solution resulted in the formation of two major and one minor components (S, F, and A). The concentration of A was always less than 10% of the total. The ratio of S to F was, however, about equal in thyroglobulin preparations which ranged in iodine content from 0.2 to 1%. The final ratios were obtained before all the disulfides were reduced. The relative mobilitis of S, F, and A, decreased with increasing extent of reduction. Fully reduced S and F, but not A, migrated slower than unreduced 12 S. The three reduced alkylated polypeptides were purified by preparative SDS-polyacrylamide gel electrophoresis and their molecular weights were determined by sedimentation equilibrium in 8 M urea. Their Mw and Mz values agreed closely with that of the unreduced 12 S half-molecule subunit, thus indicating that reduction of the disulfide bonds changes the shape but not the molecular weights of the subunits.     

The succulent flora of South Africa and Namibia: representation and distribution

Abstract

Taxonomic representation and regional distribution patterns of taxa, life forms, and defence mechanisms of the succulent flora of South Africa and Namibia are quantified and discussed in relation to physical and biotic factors. Habitats are investigated and for each region centres of succulent species richness are pointed out.     

Complementarity as a biodiversity indicator strategy

Richness, rarity, endemism and complementarity of indicator taxon species are often used to select conservation areas, which are then assumed to represent most regional biodiversity. Assessments of the degree to which these indicator conservation areas coincide across different taxa have been conducted on a variety of vertebrate, invertebrate and plant groups at a national scale in Britain, Canada, USA and South Africa and at a regional scale in Cameroon, Uganda and the USA. A low degree of spatial overlap among and within these selected indicator conservation areas has been demonstrated. These results tend to suggest that indicator conservation areas display little congruence across different taxa. However, some of these studies demonstrate that many conservation areas for indicator taxa capture a high proportion of non-target species. Thus it appears that indicator conservation areas might sample overall biodiversity efficiently. These indicator conservation areas may, however, exclude species essential for effective conservation, e.g. rare, endemic or endangered species. The present study investigated the value of indicator taxa as biodiversity surrogates using spatial congruence and representativeness of different indicator priority conservation areas. The conservation status of species excluded by the indicator approaches is also assessed. Indicator priority conservation areas demonstrate high land area requirements in order to fully represent non-target species. These results suggest that efficient priority area selection techniques must reach a compromise between maximizing non-target species gains and minimizing land-use requirements. Reserve selection procedures using indicator-based complementarity appear to be approaches which best satisfy this trade-off.     

An evaluation of the gradsect biological survey method

Biological surveys are necessary to gather species distribution data for the identification of priority conservation areas. The rationale of the gradsect method is that sampling (transects) oriented along the steepest environmental gradient should detect the maximum number of species in an area. The efficiency of the gradsect survey method was evaluated by comparing it to random, systematic and habitat-specific survey methods, during faunal field surveys (target groups: birds and dung beetles). Three gradsects were positioned within the study area to follow the major physiographical characteristics, incorporate all environmental strata (land facets) and yet be as logistically convenient as possible. The efficiency of survey methods was expressed as the number of species recorded per sampling unit effort and illustrated using bootstrap estimations to plot species accumulation curves. The gradsect method proved to be as efficient as the habitat-specific survey method and consiste ntly more efficient than the systematic and random surveys for both taxa sampled. The present study therefore illustrates that the gradsect survey method provides a cost-effective and swift representative sample of regional fauna. Moreover, the results indicate that land-form sequences, specifically land facets, are useful surrogates when sampling environmental diversity where distinct environmental gradients such as altitude and rainfall are absent.     

Revisiting Green Data species lists

The management and active enforcement of the increasing number of conservation-related instruments (e.g. the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), The World Conservation Union (IUCN) Red Data Lists and pending invasive species regulations), and the number of listed plant and animal taxa that they are likely to incorporate, are already straining national regulatory, enforcement and border control agencies. Against the backdrop of increasing capacity constraints (financial and logistic) and uncertainty faced by these authorities, we support calls for a radical shift in the traditional approach to the management of threatened species (either Red Data List or CITES listed) and the maintenance of the integrity of biological systems (viz. the control of potentially invasive species). This entails the establishment of National Green Data Species Lists (proposed by Imboden (1989) in World Birdwatch 9:2). The Green List would be a reciprocal list of species that are not threatened (not Red Data listed), not affected by trade (not CITES listed) or pose little threat of invasion according to importing authorities. This reciprocal list does not require negotiation of new international treaties and will simply piggy-back on existing treaties. In addition, it will shift the 'burden of proof', including the financial investment required for species Green Data listing, the verification of origins, taxonomic and conservation status determination, from regulating authorities to traders.     

Perceived Stress and Weight Gain in Adolescence: A Longitudinal Analysis

Although perceived stress has been hypothesized to be a risk factor for obesity, epidemiological studies relating stress to weight gain have shown mixed results. We examined prospective associations between perceived stress and changes in waist circumference and BMI in a large study of adolescents. As part of the Health and Behaviour in Teenagers Study (HABITS), height, weight, and waist circumference were measured annually in 4,065 adolescents aged from 11 to 16. Waist and BMI standard deviation scores (SDS) were used as indices of adiposity. Adolescents completed a measure of perceived stress each year, from which mean stress scores over the 5‐year period were also calculated and divided by tertile into lower, moderate, and higher stress. Associations between perceived stress at each year and adiposity 1–4 years later and also adiposity trajectories over the whole period in relation to mean stress were investigated. Analyses were adjusted for age, sex, ethnicity, socioeconomic deprivation, pubertal timing, and smoking. Perceived stress in any year was not related prospectively to increases in waist or BMI SDS 1–4 years later, nor was there any evidence that higher stress over the whole period was associated with greater gains in waist or BMI SDS. However, waist and BMI SDS were significantly higher in the moderate‐ and higher‐stress groups than the lower‐stress group across the whole 5‐year period. Persistent stress was associated with higher waist circumference and BMI in adolescence, but did not lead to differential changes over 5 years.     

Conservation strategies for poorly surveyed taxa: a dung beetle (Coleoptera, Scarabaeidae) case study from southern Africa

Despite being the focus of an international research effort spanning decades, the spatial distribution of southern African scarab beetles remains poorly documented. As well as reinforcing the magnitude of the challenge facing biodiversity scientists, this raises real concerns about best practice conservation strategies in the absence of detailed distribution information. However, dung beetles appear to be well represented in established conservation areas. This apparent contradiction could be ascribed to anthropogenic transformation, successful conservation efforts, the presence of dung generalists and reserve-biased or mesic-biased dung beetle collection efforts. It is suggested that all of the above contribute to the observed pattern to varying degrees. The implications of selecting areas that are either rich in species, contain rare species or contain taxonomically distinct species from a group whose taxonomy is well known but for which inadequate distribution data exist are explored. Best practice, in the face of inadequate data, appears to revolve around a subtle interplay between advantages and disadvantages associated with data interpolation techniques, reserve selection algorithms that use criteria more robust than database rarity (such as taxonomic distinctiveness) and the long-term economic costs of proceeding with the data at hand versus investing in biological surveys.